The daffodil-colour rock is mounted as a ring and sparkles with “extraordinary fire and brilliance,” according to the auction house, which added the auction, featuring two diamonds over 100 carats, drew buyers from more than 30 countries.

Previously known as the Dream Diamond, the Graff Vivid Yellow was a captivating 190-carat rough stone at the time Laurence Graff — a high-profile connoisseur and collector of fine coloured diamonds— bought it in Kimberley, South Africa. When he first saw the diamond crystal, he stated, “It was an intense golden yellow and one of the rarest yellow diamonds I had ever seen. I knew the polished stone within would be more than exceptional.”

The rock was then sent to the Gemological Institute of America (GIA) to certify its natural authenticity. For the next nine months, New York master cutter Nino Bianco transformed the stone. The brilliant, 100.09-carat polished cushion-cut diamond was renamed the Graff Vivid Yellow and was unveiled as the world’s largest yellow diamond. It made its public debut at Kensington Palace in London.

Today’s sale came only a few hours before Christie’s puts “The Blue” on sale. The 13.22 carats gem, considered the largest flawless vivid blue diamond in the world, is expected to fetch up to $25 million.

While the auction house would not reveal the diamond’s owner, it said it had been in the holder's possession for a long time.

Another unique stone to be sold off on May 14 is the "Ocean Dream", a fancy vivid blue-green triangular-cut diamond ring weighing 5.5 carats and worth at least $7.8 million.

If recent auctions in Geneva are any indication, “The Blue” could fetch more than $25 million. When the world's largest orange diamond, a 14.82-carat gem called "The Orange", which went under the hammer last November, was sold for $35.5 million more than double its $17-20 million price tag.

From the two auction houses Sotheby’s is the one that holds the world record price for a diamond sale. That happened in November 2010, when it sold the 24.78-carat “Graff Pink” rock for $46 million, also in the Swiss capital.